Why 04 Aero VT750 Takes 4 Spark Plugs ?


Can anyone tell me why my ’04 Aero vt750 takes 4 spark plugs ? I thought two cylinder heads, two spark plugs.

Gregory 6 years 25 Answers 2162 views 0

Answers ( 25 )

  1. 4 one on each side

  2. That dates back to first conception. My first Shadow was an 83 Vt500c and she had 4 spark plugs (2 per cylinder) Im guessing it’s performance and economy reasons.

  3. “Twin spark” provides uniform combustion to improve performance and lowering emissions and consumption.

  4. This makes perfect sense now. Back to the bike shop to buy another two plugs ?

  5. I stand to be corrected but the second plug burns any unburnt fuel before emission, hence the “Twin spark”.

  6. Dual spark system.

  7. One plug fires slightly after and burns unspent fuel. More power better mileage.

    • Hmm didn’t think this was possible tho,,seeing how it the same coil with 2 wires, wouldn’t you need a 2nd coil running off if a different pickup sensor for delayed timing on spark vs the one with accurate timing? ??

  8. There are several cars made this way as well. Its not weird.

  9. It’s a great design and nice that it comes “stock” on the Hondas. Back in the ’80s we spent big bucks to have that second plug installed on the old air-head BMWs. It was an expensive and popular performance upgrade.

  10. Part of the combustion chamber is shrouded by the valves, a second plug ensures a complete burn.

  11. Love my v-twin 4 plug aero!

  12. Because the Japanese know how to make good stuff.

  13. One for intake and one for exhaust side of head helps with power and cleaner burning exhaust same as ford ranger.

  14. Emmissions. Better burn of fuel with two plugs per cylinder.

  15. Our V8 Mercedes has 16 spark plugs, probably the same reason.

  16. I was to by a motorcycle mechanic the reasoning for 4 plugs is that the pistons are somewhat tapered, and in order for it to get good compression you need 2 plugs per side.

  17. Pistons are never tapered. Compression has nothing to do with number of plugs.

  18. it helps with combustion of all the fuel.

  19. My old 1984 Nissan truck had 8 plugs on a 4 cyl. I asked a seller on ebay why he gave 4 compression rates. He thought the engine had 4 pistons, funny as all 4 readings were different.

  20. 10 years I had my shadow only ever changed 3 till me and big brother found the 4th hiding under the tank ….

  21. The 2nd plug on each cylinder is to burn excess gas for cleaner emissions and less fuel waste.
    Its same concept for cars.

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